Shielding apparatus for an electrical assembly

BACKGROUND OF THE INVENTION

The present invention is directed to a shielding apparatus for an electrical assembly insertable into a module magazine. It is known to manufacture front covers for an electrical assembly out of metal and to fasten thereto thin contact plates that are provided with lateral contact tabs. These contact tabs are fashioned such that they press against the front cover of a neighboring assembly. The grounded front covers, together with the contact plates, enable a gap-free electrical shielding of the assemblies along their front side.

Modern electronic circuits operate with extremely high clock rates and require a shielding. Since the front covers in the row of assemblies are electrically connected in series, a low surface transfer impedance between the front covers is necessary. This requirement of low impedance is degraded in that the front covers and the contact plates are typically composed of different materials, which leads to electrical corrosion, and in that two electrical junctions are present per each front cover.

SUMMARY OF THE INVENTION

An object of the present invention is to reduce the electrical resistance and the manufacturing outlay related to shielding apparatus for electrical assemblies.

This object is achieved by the present invention of a shielding apparatus wherein a strip-shaped contact plate is secured to the front cover of the electrical assembly. This contact plate extends in the longitudinal direction of the front cover and has a plurality of resilient contact tabs positioned toward neighboring front covers. These contact tabs are contacted by the shielding apparatus of the neighboring assemblies. The contact plate, fashioned as a shroud, covers the entire front cover and is directly contacted by the shrouds of the two neighboring assemblies. Since a given shroud is now directly contacted by the neighboring shrouds, the number of electrical junctions per front cover is reduced over prior art devices. Respectively identical materials are in contact with one another and reduce the risk of electrical corrosion. Also the contact resistances are considerably reduced as a result thereof, so that any arising noise currents can be more effectively eliminated.

Since the shroud covers the entire front cover, it can be held on the front cover in a simple manner with the use of a suitable catch means, so that the assembly outlay is correspondingly reduced. Also a significant advantage is that the front cover can now be made of plastic since it is no longer required for the shielding or electrical connection, thereby reducing manufacturing costs.

The contact tabs are arranged along one long side of the shroud with cooperating contact locations which are non-resiliently fashioned. Thus, the arrangement of the non-resilient contact locations in a defined plane establishes uniform contact conditions.

Greater possibilities of variation with respect to the design of the contacts results from the contact tabs being provided on both long sides of the shroud.

Greater spacing tolerances between the front covers can be compensated for by the contact tabs of two neighboring shrouds contacting one another.

In a further embodiment the resilient contact tabs and non-resilient contact locations are arranged in alternating succession on every long side of the shroud, one contact tab of a shroud contacting a non-resilient contact location of the neighboring shroud and the non-resilient contact locations being broader than the resilient contact tabs. This provides a tight interleaving of the contact tabs with the non-resilient contact locations given a high number of contacts having a corresponding large contact surface.

Identical shrouds in the same orientation can be attached to all front covers due to one contact tab of one long side of the shroud lying opposite a non-resilient contact location of the other long side.

Furthermore, the contact tabs can be mirror-symmetrically arranged on both long sides of the shroud. This structure can be employed in both types of contacting. In the combination of resilient contact tabs with stationary cooperating contact locations, the contact tabs are respectively offset by half a division from assembly to assembly. This can be beneficially achieved in that the shroud has a contact tab at one end and a stationary contact location at the other end, and in that the shrouds are secured to the front covers in alternating orientation. When, however, a contact from contact tab to contact tab is desired, then the shrouds are secured to the front covers in the same orientation.

The shroud can be snapped onto the front cover with retaining tabs whose resilient ends engage behind the front cover. This utilizes the spring properties of the shroud for the fastening to the front cover as well.

The retaining tabs can be arranged in the interspaces between the contact tabs. This yields a great plurality of retaining tabs so that the forces occurring when pulling the assembly are reliably intercepted.

Also the retaining tabs can be especially utilized as contact locations in that the retaining tabs server as non-resilient contact locations.

The contact tabs can be bent back onto themselves in the fashion of a semicircle to provide good spring properties.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the present invention which are believed to be novel, are set forth with particularity in the appended claims. The invention, together with further objects and advantages, may best be understood by reference to the following description taken in conjunction with the accompanying drawings, in the several Figures in which like reference numerals identify like elements, and in which:

FIG. 1 is a perspective view of a part of two neighboring assemblies having front covers and shrouds; and

FIG. 2 is a plan view of the parts of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

According to FIGS. 1 and 2, two electrical assemblies are inserted into a magazine (not shown). The assemblies have printed circuit boards 1 to whose front sides are attached front covers 2 which are formed of plastic. Shrouds 3 are snapped onto the front covers 2. Shrouds 3, that are essentially bent into a u-shape have retaining tabs 4 and contact tabs 5 in alternating succession on each of their long sides, these retaining tabs 4 and contact tabs 5 having been produced by shearing and different bending. The contact tabs 5 thereby project beyond the retaining tabs 4. The tabs 5 are mirror-symmetrically arranged on both long sides of the shroud 3.

The shroud 3 extends over the entire length and width of the front cover 2. The contact tabs 5 are contacted by contact tabs 5 of a neighboring assembly. As result, the entire front side of the fully equipped magazine is covered in sealed radio-frequency fashion.

The retaining tabs 4 are perpendicular to the front side of the assemblies. The free end of each of the retaining tabs 4 is bent toward the front cover 2 and engages behind the front cover 2 at a corresponding latch shoulder 6. The front cover 2 is provided with lateral leading bevels 7 for the retaining tabs 4.

The contact tabs 5 are bent semicircularly back onto themselves and project beyond the front covers 2 in the direction of the neighboring front covers to such an extent that they press resiliently against the contact tabs of the neighboring shrouds 3. A large-area contact between the shrouds 3 is thus established due to the multitude of contact tabs 5.

If the contact tabs 5 of one shroud 3 and the retaining tabs 4 of the neighboring shroud 3 are staggered relative to one another (as can be derived from FIG. 1), then the contact tabs 5 of the one shroud 3 will contact the retaining tabs 4 of the neighboring shroud 3. The retaining tabs 4 then become contact locations which are non-resilient.

The invention is not limited to the particular details of the apparatus depicted and other modifications and applications are contemplated. Certain other changes may be made in the above described apparatus without departing from the true spirit and scope of the invention herein involved. It is intended, therefore, that the subject matter in the above depiction shall be interpreted as illustrative and not in a limiting sense.